Freescale Semiconductor PowerQUICC MPC885 Reference Manual page 875

Table 31-15 describes USB TxBD fields.
Offset Bit Name
0x00 0 R
1 —
2 W
3 I
4 L
5 TC
6 CNF
7 LSP
8–9 PID
10 —
Freescale Semiconductor
Table 31-16. USB Host TxBD Fields
Ready
0 The data buffer associated with this BD is not ready for transmission. The user is
free to manipulate this BD or its associated data buffer. The CP clears this bit after
the buffer has been transmitted or after an error condition is encountered.
1 The data buffer, which has been prepared for transmission by the user, has not
been transmitted or is currently being transmitted. No fields of this BD may be
written by the user once this bit is set.
Reserved, should be cleared.
Wrap (Final BD in Table)
0 This is not the last BD in the TxBD table.
1 This is the last BD in the TxBD table. After this buffer has been used, the CP will
send data using the first BD in the table (the BD pointed to by TBASEx). The
number of TxBDs in this table is programmable, and is determined only by the
TxBD[W] and the overall space constraints of the dual-port RAM.
Interrupt
0 No interrupt is generated after this buffer has been serviced.
1The TXB or TXE bit in the event register is set when this buffer is serviced. TXB and
TXE can cause interrupts if they are enabled.
Last
0 Buffer does not contain the last byte of the message.
1 Buffer contains the last byte of the message.
Transmit CRC. Valid only when the L bit is set; otherwise it is ignored. Prepare TC
before sending data.
0 Transmit end-of-packet after the last data byte. This setting can be used for testing
purposes to send a bad CRC after the data.
1 Transmit the CRC sequence after the last data byte.
Transmit confirmation. Valid only when the L bit is set; otherwise it is ignored. Applies
to multi-frame enabled endpoints (USEP n [MF] = 1); see
Endpoint Registers (USEP0–USEP3)."
0 Continue to load the transmit FIFO with the next packet. No handshake or
response is expected from the function for this packet.
1 Wait for handshake or response from the function before starting the next packet,
or this is the last packet.
Do not clear CNF for a token preceding a data packet unless the data packet's BD is
ready.
Low-speed transaction. Use for tokens only.
0 The following transaction is with the host or a full-speed device.
1 The following transaction is with a low-speed device. Required only for tokens.
Note that LSP should always be cleared in slave mode.
Packet ID. This bit field is valid for the first BD of a packet; otherwise it is ignored.
0X Do not append PID to the data.
10 Transmit DATA0 PID before sending the data.
11 Transmit DATA1 PID before sending the data.
Reserved, should be cleared.
MPC885 PowerQUICC Family Reference Manual, Rev. 2
Universal Serial Bus (USB)
Description
Section 31.11.3, "USB
31-27